This invention relates generally to boring machines, and more particularly to boring machines having elongated boring bars for internal end boring of a pipe end or other elongated workpieces.
Many elongated workpieces such as pipes, tubing, or rods, have to be end bored internally before use. For example, referring to my co-pending U.S. Pat. Application Ser. No. 20,366 which was filed on Mar. 14, 1979, for Method and Apparatus For Simultaneously Boring and Turning Upset Pipe Ends, now U.S. Pat. No. 4,289,430 issued Sept. 15, 1981 it is therein described that many pipes, when manufactured, have upset or thickened pipe ends which must have their inside and outside diameters machined or bored and turned before they can be used in the field to connect adjacent pipe sections. In that application, I describe a novel machine which simultaneously bores and turns such upset pipe ends.
When internally end boring such elongated workpieces as upset pipe ends, it is necessary to utilize an elongated boring bar having cutting or boring tools on the boring or free end thereof. Due to the length and flexibility of the boring bar and of the workpiece being bored, the boring bar, and for that matter, the workpiece, chatter and vibrate during initial end boring operations causing inaccurate boring cuts and excessive wear and damage to the boring tools and the inside surface of the workpiece being bored. In an attempt to avoid this problem, many boring machines of the prior art have incorporated boring bars which are made of special rigid metal. However, such boring bars are excessively expensive and in addition they do not totally solve the problem, as chattering or vibration on initial boring nevertheless still occurs, even if to a lesser degree.
A more recent attempt to solve this problem was carried out by using an axially slidable rigidizing collar which is coaxially carried over the boring bar and slid rearwardly or axially along the boring bar by the pipe end as the end boring operation advances. In this prior art apparatus, a cylindrical housing is coaxially mounted over and spaced from the boring bar, and rotates with the boring bar, then a sleeve is slidably received coaxially over the boring bar between the cylindrical housing and the boring bar. This sleeve is provided with a snug sliding fit between it and the boring bar and the sleeve and the outer cylindrical housing so that the sleeve during initial end boring operations of an elongated workpiece may be advanced very close to the free or boring end of the boring bar to rigidly hold or stabilize the boring bar during initial end boring operations. As initial end boring of the elongated workpiece or pipe advances, the pipe end engages this sleeve and slides it rearwardly back against a fluid pressure thereby continually exposing more free end of the boring bar for advanced internal boring of the pipe end. While this mechanism does assist in helping to rigidize the boring bar during initial end boring operations, nevertheless, many deficiencies remain.
For example, the rigidizing sleeve coaxially received over the boring bar must be provided with necessary slide clearance between the sleeve and the bar, and it can be readily seen that with continued use, the clearance necessarily becomes larger with wear, thereby permitting the bar to vibrate or chatter. In addition, dirt, metal cuttings, etc. find their way into this clearance causing the sleeve to slidably bind onto the boring bar, thereby causing maintenance, down time, and the boring bar surface becomes scarred after use. A scarred boring bar will eventually have to be replaced and will also cause the situation wherein the rigidizing sleeve will again bind on the scarred bar surface.
With such prior art boring machines, it must also be remembered that the pipe end being bored is stationary while the boring head together with the rigidizing sleeve are rotating. This means that a bearing surface must additionally be provided between the rotating face of the rigidizing sleeve where the pipe end butts up against it. It is thus obvious that end finishing or pre-machining of the end of the pipe is desirable in order to minimize this problem, thus requiring additional costly machining operations preparatory to end finishing of the pipe.
Another problem encountered with this boring machine of the prior art is that the coaxially slidable rigidizing sleeve previously explained must coaxially slide over the boring bar for practically its entire length and therefore there is no room on the machine behind the boring head to mount other pipe end facing and/or chamfering tools on the machine head for successive machining operations on the pipe end. Thus, this machine of the prior art makes it necessary to utilize additional expensive machinery for such end facing and chamfering operations.
It is a principal object of the present invention to completely eliminate these aforedescribed disadvantages of the prior art.